Many integrated circuits including central processing units (CPUs) may be damaged if operated at too high a temperature. For example, an integrated circuit if overheated can reduce the life-span of the circuit and may interfere with proper operation. A variety of techniques have been proposed or utilized to dissipate the heat generated by such computer components. For example, heat sinks have been used to increase the surface area which dissipates the heat. A heat sink is frequently a block of metal machined to have a number of fins and ridges to increase its surface area. An adhesive or clamp may be used to affix the heat sink to the package containing the integrated circuit.
Often, a thermally conductive pad, gel or paste is placed between the integrated package and the heat sink to facilitate the flow of heat from the integrated circuit to the heat sink to be dissipated. Such heat flow may be further facilitated by another heat sink internal to the package. Such internal heat sinks, often referred to as integrated heat spreaders, are disposed on the die with a layer of thermally conductive material between the heat spreader and the die. A second layer of thermally conductive material may be disposed between the internal heat sink of the package and an external heat sink. Many such external heat sinks have an attached fan to further increase heat dissipation. Integrated circuits utilizing an individual heat sink for that particular integrated circuit include CPU's, Graphic Processor Units (GPUs) and Northbridge integrated circuits.
Another technique is often referred to as “softcooling” in which the operation of an integrated circuit may be throttled down to decrease heat generation. In some integrated circuit designs, one or more thermal sensors are included on the integrated circuit die itself together with internal logic on the die which shuts down the integrated circuit if a certain temperature is exceeded or if the circuit is idle. Other softcooling techniques include internal logic circuitry which reduces the clock speed or the voltage level supplied to the integrated circuit to slow down operation and thereby reduce heat generation if it is overheating or has a relatively low workload. Another soft cooling technique shifts a thread of operation from an integrated circuit portion such as a core which is overheating to another cooler core of a multicore integrated circuit.
A heat pipe which typically includes a hollow tube containing a heat transfer liquid, may also be used to cool a computer component. For example, a CPU may have a hollow heat sink coupled by a heat pipe to a larger radiator heat sink. The liquid transfers heat from the CPU through the heat pipe to the heat sink radiator.
It has also been proposed to utilize the “Peltier effect” to cool a computer component. Jean Peltier discovered that applying a voltage to a thermocouple creates a temperature differential between two sides, providing a heat pump, often referred to as a Thermoelectric Cooler (TEC). Many thermoelectric coolers may be stacked together or laid out next to each other to provide a significant amount of heat transfer. Bismuth and telluride are commonly used for thermoelectric coolers.
One or more TECs may also be thermally coupled to an integrated circuit die to provide on-die cooling. Thin Film TEC devices (TFTEC) are a particular implementation of TEC devices that can be included under the integrated heat spreader (IHS), and positioned in the thermal interface material (TIM) that “glues” the die with the IHS. The heat removed by the Peltier effect is typically a function of the intensity of the current supplied to the TEC. However, the current generates its own heat and therefore in some devices, a practical limit may exist as to the amount of current which can be effectively applied to cool a device.